<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>child</title>
<script>
    function childFunction() {
        alert('function in child');
    }

    function callParent() {
        parent.parentFunction();
    }
</script>
</head>
<body>
<input type="button" name="call parent" value="call parent" onclick="callParent()"/>
</body>
</html>